Electric valve circuit



Oct. 29, 1940. K. HERZOG ET AL 2,219,924

ELECTRIC VALVE CIRCUIT Filed May 10, 1958 2 Sheets-Sheet 1 Synchrpscope gm! 4 a "1L 2 .J

Inventors:

Kurt Herzog,

Y Georg VaFladis,

Th eir Attorney.

Oct. 29, 1940. K, HERZQG A 2,219,924

ELECTRIC VALVE CIRCUIT Filed May 10, 1938 2 Sheets-Sheet 2 Fig.2.. b c

-TIME :TIME

UNITED STATES PATENT OFFICE 2,219,924 ELECTRIC VALVE CIRCUIT Kurt Herzog, Berlin-Charlottenburg, and Georg Our invention relates to and more particularly to Vafiadis, BerIin-T'reptow,

Germany, assignors to General Electric Company, a corporation of New York Application May 10, 1938,

Serial No. 207,032

In Germany July 2, 1937 5 Claims.

electric valve circuits excitation or control circuits for electric valve apparatus.

In excitation or control circuits for electric valve apparatus it is f requently desirable to employ both manual and automatic control means which control the conductivity of an associated electric valve apparatus.

translating apparatus Particularly, in electric comprising electric valve valve means from automatic means to the manual means.

fect this transition fr Furthermore, it is necessary to efom the automatic control means to the manual control means without causing a disturbance in an associated load circuit which may be fed by the electric valve means.

In other words, it is important to effect improved control permit a smooth manual control witho ditions during the It is an object excitation circuits which transition from automatic to ut causing transient contransfer operation. of our invention to provide a new and improved electric valve circuit.

It is another object of our invention to provide a new and improved 0 ontrol or excitation circuit for electric valve means.

It is a further object of our invention to provide a new and improved method for controlling electric valve apparatus.

In accordance with the illustrated embodiment apparatus which energizes a direct current load circuit from an alternating current supply cir- The electric valve apparatus may comprise a control member or a plurality of control members which control the conductivity of the electric valve means. system comprises aut presses on the control which vary in phase termined controlling The control or excitation omatic means which immembers periodic voltages in accordance with a predeinfiuence such as the voltage of the direct current load circuit. The control system also comprises a manually adjustable phase shifting circuit relation with the first periodic voltage which with respect to the an electric valve means.

which introduces in series periodic voltage a second may be adjusted in phase ode cathode voltage of the The automatic means may be of the type designed to produce a voltage of peaked wave form and may comprise an electric discharge device of the controlled type which periodically transmits impulses of peaked voltage to the control member or members of the 5 electric valve means. The electric discharge device is in turn controlled by a suitable circuit such as a voltage sensitive circuit or an amplifier electric valve means. When the system is arranged to control automatically the electric valve means, the phase of the manually adjustable periodic voltage is positioned so that it is substantially ineffective so far as the control of electric 15 valve means is concerned. For example, in rectifier operation this voltage is displaced substantially 180 electrical degrees relative to the anode cathode voltage. When it is desired to efiect transfer of control from the automatic to the manual means, the phase of the manually adjustable periodic voltage is advanced to substantial coincidence with the automatically controlled periodic voltage and the periodic voltage due to the automatic means is then removed. In this 25 manner the transition from the automatic means to the manual means is effected without causing a material disturbance in the output characteristic of the electric valve means.

For a better understanding of our invention reference may be had to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

Fig. 1 of the accompanying drawings diagrammatically illustrates an embodiment of our invention as applied to an electric valve rectifying system; and Fig. 2 represents certain operating characteristics thereof.

In Fig. 1 of the accompanying drawings there is diagrammatically illustrated an embodiment of our invention as applied to an electric valve sysratus comprising a transformer 3 valve means 4. A suitable circuit controlling means such as a switch 5 may be employed to connect and disconnect the translating apparatus from the supply circuit l. The electric valve means 4 is preferably of the type employing an ionizable medium such as a gas or a vapor and may comprise a pair of anodes 6 and 7 and a single mercury pool cathode 8 within an enclosing envelope 9. Control members I 0 and II are 'may be connected in series associated with the anodes 6 and 1, respectively, and control the conductivities of the associated arc discharge paths which are provided by the anodes 6 and I and the cathode 8. As a means for initiating ionization of the medium, which in the embodiment illustrated is mercury vapor, we may employ a suitable electrode |2 upon which there is impressed a suitable potential by apparatus not shown. The electric valve means 4 may also comprise holding anodes l3 and M which are energized by a circuit, not shown, to maintain the mercury vapor As a means for controlling the conductivity of the electric valve means 4, we provide an excitation circuit H: which comprises an automatic means l6 and a manual means ll. The automatic means I6 impresses on control members I0 and II periodic voltages automatically variable in phase in accordance with a predetermined controlling influence such as an output characteristic or the output voltage of the electric valve means 4. The automatic means l6 may be energized from any suitable source of alternating current correlated in phase and frequency relative to the voltage of the alternating current circuit In the embodiment shown in Fig. l, the automatic means I6 is represented as being energized from the alternating current circuit I through a switch I8. The automatic means I6 comprises a transformer l9 having a primary winding 20 and secondary windings 2 |-24. The periodic voltages of the automatic means l6 are impressed on the control members Ill and II of electric valve means 4 through transformers 25 and 26. In order to control the phase of the periodical voltages produced by the automatic means I6 in accordance with the voltage of circuit 2, we provide electric discharge devices 21 and 28 which are preferably of the type employing an ionizable medium such as a gas or a vapor and each comprises an anode 29, a cathode 30 and a control grid 3|. The electric discharge devices 21 and 28 are associated with and receive power from secondary windings 2| and 23, re-

spectively, of transformer l9.

The conductivities of the electric discharge devices 21 and 28 are controlled by control circuits 32 and 33, respectively. These circuits vary the time during the cycles of anode-cathode voltage of electric valve means 4 at which the electric discharge devices 21 and 28 are rendered conductive, and hence control the output voltage of the electric valve means 4. The control circuits 32 and 33 each includes a phase shifting means which may be of the static-impedance type comprising a capacitance 34 and a resistance 35. Current limiting resistances 3B relation with the control grids 3| of electric discharge devices 21 and 28. The control circuits 32 and 33 are designed by proportioning of the capacitances 34 and resistances 35 so that the alternating components of voltages impressed on the control grids 3| are substantially retarded in phase relative to the anode-cathode voltages of the electric discharge devices 21 and 28. This angle of retardation may be substantially 90 electrical degrees. As a means for controlling the conductivities of the electric discharge devices 21 and 28in response to an electrical condition of circuit 2 such as the volt-age of circuit 2 we employ a suitable means such as an amplifier 31 or other voltage sensitive device which impresses on the control grids 3| a unidirectional voltage which varies in magnitude in accordance with in an ionized state.

the departure of the voltage of circuit 2 from a predetermined value. This unidirectional potential may vary throughout positive and negative ranges and may vary in magnitude in accordance with the voltage of circuit 2. Of course, the resultant voltage impressed on the control grids 3| is the sum of the alternating component and the unidirectional component so that the resultant voltage impressed on the grids 3| varies in phase in accordance with the voltage of circuit 2 Where it is desired to impress on the control members Ill and H of the electric valve means 4 voltages of peaked wave form, we may employ parallel connected capacitances 38- and resistances 39 which are connected in series relation with the electric discharge devices 21 and 28. When the electric discharge devices 21 and 28 are rendered conductive, impulses of current are transmitted through the primary windings of transformers 25 and 26 thereby inducing relatively large voltages of peaked wave form in the secondary windings. Although a particular type of circuit for producing voltages of peaked wave form is employed, it will be well understood by those skilled in the art that other types of circuits well known in the art for accomplishing this result may be employed without departing from our invention in its broader aspects.

The manually adjustable means |l comprises a phase shifting circuit 40 which may be energized from a suitable source of alternating current such as circuit I through a transformer 4|. The phase shifting circuit 40 may be of the static-impedance type comprising a capacitance 42 and a manually adjustable resistance 43. The output voltage of the phase shifting circuit 40 is impressed on the control members l0 and H of electric valve means 44 have a primary winding 45 and a. secondary winding 46. It will be noted that the secondary winding 46 is connected series relation with the secondary windings of transformers 25 and 26 so that the two periodic voltages effectively act in series relation. Current limiting resistances 4'! may be connected in series relation with the control members l0 and II of electric valve means 4. i

To provide an indication of the phase'relationship between the periodic voltage produced by the manual means I! and the periodic voltage produced by 'the automatic means Hi, we employ any suitable and conventional arrangement such as a synchroscope 48 which is connected to the output circuit of the manual-.means l1 and to one of the output circuits of the automatic means 16.

The operation of the embodiment of our invention diagrammatically illustrated in Fig. 1 of the drawings will be explained by considering the system when direct current is being supplied to the load circuit 2 from the alternating current supply circuit I through transformer 3 and electric valve means 4. The output voltage of circuit 2, of course, may be controlled by controlling the conductivity of the electric valve means 4. It is understood by those skilled in the art that the voltage of circuit 2 is maximum when the arc discharge paths are rendered conductive near the beginning of the positive half cycles of anode-cathode voltage and that the output voltage of the electric valve means decreases as the electric valves are rendered conductive at later points in the positive half cycles. 26

When the system is arranged for automatic operation, the automatic means I6 is energized from the alternating current circuit I and the switch 18 is maintained in the closed circuit position. Electric discharge devices 21 and 28 are rendered conductive alternately to produce periodic voltages of peaked wave form which are impressed on the control members and II by way of transformers 25 and 26. The phase of the impulses of the periodic voltage of peaked wave form produced by circuit I6 is controlled by the control circuits 32 and 33 and the amplifier 31. When the electric discharge devices 2'! and 28 are rendered conductive, impulses of current of relatively large magnitude are transmitted through the primary windings of transformers 25 and 26 to generate periodic voltages of peaked Wave form which are impressed on control members II) and II. The positive unidirectional biasing potential may vary in sign and magnitude in response to the voltage of the direct current circuit 2 to maintain the voltage of circuit 2 substantially constant.

The manual means l1, during the time when the automatic means is effectively controlling the conductivity of electric valve means 4, is adjusted so that the output voltage is substantially ineffective, that is, is adjusted so that the voltages derived from the phase shifting circuit 40 are substantially 180 electrical degrees out of phase with the anode-cathode voltages of electric valve means 4. When it is desired to effect transfer of the control of electric valve means from automatic to manual operation, the phase of the manually adjustable periodic voltage is advanced by adjustment of the resistance 43 to a position in which there is substantial phase coincidence between the output voltages of circuit I! and the periodic voltages of the automatic means Hi. This position of substantial phase coincidence may be detected by observance of the synchroscope 48. When such a condition of phase coincidence is established, the switch I8 may be opened thereby rendering ineifective the automatic means l6.

For a better understanding of the manner in which our invention operates, reference may be had to the operating characteristics shown in Fig. 2. Curve A represents the anode-cathode voltage for one of the arc discharge paths of electric valve means 4, for example, the arc discharge path between anode 6 and cathode 8. Curve B represents the critical voltage control characteristic for the electric valve means 4, that is, the voltage which must be impressed on the control member to render the discharge path conductive. Curve 0 represents the phase of the output voltage of the manual means I! when the system is under the control of the automatic means I 6. Curve D represents the anode-cathode voltage of the electric discharge device 28 and curve E represents the critical control voltage for this electric discharge device. Curve F represents the resultant voltage impressed on grid 3! of electric discharge device 28 by control circuit 33 and the distance a represents the magnitude of the unidirectional biasing potential produced by the amplifier 31 which effects the shifting in phase of the resultant voltage impressed on the grid 3!. Curve G represents the resultant voltage impressed on the grid 3| of the discharge device 28 when the unidirectional biasing potential is substantially zero.

For the particular conditions represented by curves D, E and F, the electric discharge device 28 will be rendered conductive at time b when the resultant voltage impressed on the grid 3|, as represented by curve F, intersects the control characteristic curve E. Due to this action, there is generated in the secondary winding of transformer 25 a voltage of peaked wave form as represented by curve H. The voltage of peaked wave form is, of course, impressed on control member [0 of electric valve means 4 and is effective to render the electric valve means 4 conductive at time b. The electric discharge device 28 may be rendered conductive at a later time, for example, time c by impressing a negative unidirectional biasing potential on the grid 3!, under which condition the voltage of peaked wave form will occur at about the same time. It is to be understood that the automatic control means It controls the phase of the voltage of peaked wave form as represented by curve H relative to the anode-cathode voltage as represented by curve A so that the output voltage of the electric valve means 4, or the voltage of circuit 2, remains substantially constant.

When it is desired to effect transfer of the control of electric valve means 4 from the automatic means It to the manual means H, the phase of the output voltage of circuit ll is advanced from the angle d to the angle 6 which is a position of substantial phase coincidence with the control voltage of the automatic means l6. In other words, the two periodic voltages provided by the manual means i! and the automatic means l6 are acting substantially simultaneously and concurrently to render the electric valve means 4 conductive. This position of substantial phase coincidence of the periodic voltages of the manual means I! and the automatic means I 6 may be determined by observance of the synchroscope 48. When phase coincidence is established, switch l8 may be opened so that the automatic means I6 is deenergized. The system is then arranged for manual control. Due to the fact that the transition from automatic control to manual control is effected at a time when the two periodic voltages are in phase coincidence, the conductivity of the electric Valve means 4 will not be changed abruptly and there will be substantially no disturbance caused thereby.

While we have shown and described our invention as applied to a particular system of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from our invention, and we, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a control system for an electric valve means having an anode, a cathode and a control member for controlling the conductivity thereof and having an associated excitation circuit comprising manual and automatic means for introducing into the excitation circuit separate periodic voltages which are impressed on the control member, the method of efifecting transition from the automatic to the manual control means which comprises shifting the phase of the periodic voltage of the manual means to substantial coincidence with that of the automatic means and subsequently removing the periodic voltage produced by the automatic means.

2. In combination, an alternating current circuit, a load circuit, electric translating apparatus interconnecting said circuits and comprising an electric valve means having an anode, a cathode and a control member for controlling the conductivity thereof, an excitation circuit for energizing said control member, a control circuit for introducing into said excitation circuit a periodic voltage which varies in phase in accordance with an electrical condition of said load circuit, and manual means comprising a phase shifting circuit for introducing into said excitation circuit a second periodic voltage adjustable in phase to permit transition from automatic operation to manual operation.

3. In combination, an alternating current circuit, a load circuit, electric translating apparatus interconnected between said circuits and comprising an electric valve means having an anode, a cathode and a control member for controlling the conductivity thereof, an excitation circuit for energizing said control member comprising an electric discharge device for impressing on said control member a periodic control voltage, means for controlling the phase of said periodic voltage in accordance with an electrical condition of said load circuit, and manually adjustable means for introducing into said excitation circuit a second periodic voltage to permit transfer of the control of said electric valve means from automatic to manual operation.

4. In combination, an alternating current circuit, a load circuit, electric translating apparatus interconnecting said circuits and comprising an electric valve means having an anode, a cathode i and a control member, an excitation circuit for energizing said control member and comprising an electric discharge device for generating a periodic voltage of peaked wave form, said electric discharge device being provided with a grid for controlling the conductivity thereof, means responsive to an electrical condition of said load circuit for impressing on said grid 2. unidirec-- tional potential to control the phase of said periodic voltage of peaked wave form relative to the anode-cathode voltage of said electric valve means, and manually adjustable means for introducing into said excitation circuit a second periodic voltage adjustable in phase to permit transition of said electric valve means from automatic to manual operation.

5. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus interconnecting said circuits and comprising an electric valve means having an anode, a cathode and a control member, an excitation circuit for said control member, means for introducing into said excitation circuit a periodic voltage of peaked Wave form and comprising an electric discharge device and a capacitance which is charged by said electric discharge device, said electric discharge device being provided with a grid for controlling the conductivity thereof, a control circuit for energizing said grid and comprising a source of alternating voltage and means for impressing on said grid a unidirectional potential which varies in accordance with an electrical condition of said direct current circuit, and means energized from said alternating current circuit for introducing into said excitation circuit a voltage of substantially sinusoidal wave form adjustable in phase, means for advancing the phase of said alternating voltage of sinusoidal wave form to substantial phase coincidence with the periodic voltage of peaked wave form, and means for deenergizing said electric discharge device.

KURT HERZOG. GEORG VAF'IADIS 

